WASHINGTON -- Harry Reid isn't known for hyperbole. The soft-spoken Senate majority leader tends to wield his power behind the scenes, and when he does speak at his weekly press briefing, reporters lean in and bend their ears to make out the words.

But if Reid is lied to, all that changes. It may sound dissonant to the public to say that honesty is the mostly highly valued quality in Washington. But while members of Congress may lie to their constituents with regularity, lying to one another is considered an unforgiveable sin.

In an interview with The Huffington Post, the Nevada Democrat savaged Bill Magwood, a member of the Nuclear Regulatory Commission, when asked if he thought the Democrat had a chance to become NRC chairman.

"You know, when you're in this government, this business of politics, the only thing that you have is your word," said Reid, seated in his Capitol office. "I can be as partisan as I have to be, but I always try to be nice. I try never to say bad things about people. Bill Magwood is one of the" -- Reid paused, deciding which adjective to reach for, before picking them all -- "most unethical, prevaricating" -- he paused again, this time for 10 full seconds -- "incompetent people I've ever dealt with. The man sat in that chair -- right there -- and lied to me. I've never, ever in my life had anyone do that. Never."

Magwood didn't respond to a request for comment left with his assistant.

Reid is a vociferous opponent of storing nuclear waste in Nevada's Yucca Mountain. By backing Obama early in his campaign for president, he persuaded the candidate to promise to block the project. A former staffer of Reid's was named chairman, and Reid said he was assured by Pete Rouse, a senior White House official, that Magwood would also oppose Yucca. Instead, according to Reid and confirmed by sources familiar with the internal dynamics of the NRC, Magwood worked against the effort to shut down Yucca.

"That man I will never, ever forget what a treacherous, miserable liar he is. I met with him because Pete Rouse asked me to meet with him. I said, 'Is he OK on Yucca Mountain?' Pete said, 'Yeah.' So I went through some detail with him as to how important this was to me. 'Senator, I know this industry like the back of my hand. You don't have to worry about me,' [Magwood said]. And the conversation was much deeper than that."

Late in 2011, HuffPost reported that Magwood was working with Republicans and the nuclear industry to oust then-NRC Chairman Greg Jaczko, just as he had done to his boss Terry Lash at the Department of Energy in the 1990s.

"What I eventually found was that he had been deceptive and disloyal," Lash said of his then-number two, when told what Reid said. "I'm surprised at the strength of it, but it's certainly consistent with what I've seen."

Reid and Lash have company in their critique of Magwood. In the earlier story about Magwood and the industry, multiple people who've worked closely with him questioned his integrity, but none did so on the record like Reid and Lash:

Magwood built a reputation at the Department of Energy as a sharp-elbowed operator. "He was a consummate inside player, a bureaucratic power player of the first order," recalled a former Department of Energy colleague, who, like many others interviewed for this story, requested anonymity because his current work has him interacting regularly with industry clients.

But that level of ambition is hard to contain over a long period of time in a relatively small industry. Every source to whom HuffPost spoke for this story referred to other players, whether friends or foes, by their first names. Magwood never understood it's a small world. "He always struck me as a guy who thought he was playing in a bigger political pond than he was. I mean, there are about 50 people here in town who care about nuclear energy. So it seemed like a lot of politics for no good reason," said one Democratic lobbyist who worked in the Senate while Magwood served in the Department of Energy.

Reid's public rebuke makes it nearly impossible for Magwood to attain the chairmanship. Even if Reid leaves the Senate, it would be difficult for Magwood to overcome such a judgment having been rendered.

In June, Magwood's internal wrangling against Jaczko culminated in the chairman's resignation. Magwood was immediately floated as a replacement chairman, but the Obama administration, aware of Reid's opinion of Magwood, passed him over. The term of the new chair, Allison Macfarlane, ends in 2013.

Reid said that Magwood's behind-the-scenes maneuvering was unforgivable. "He's a first-class rat. He lied to Rouse, he lied to me, and he had a plan. He is a tool of the nuclear industry. A tool," Reid said. "Magwood was a shit-stirrer. He did everything he could do to embarrass Greg Jaczko." Reid has donated $10,000 to help Jaczko pay the considerable legal bills he racked up defending against Magwood's allegations.

Jaczko was "the first chair that has never been part of the nuclear industry," Reid said, explaining the intense opposition. "That commission was a tool to the nuclear industry. Greg Jaczko, this young guy, he of course worked for me. He was against Yucca Mountain. But they knew that going in."

Reid can tolerate ideological or political disagreement, he said, as long as his opponent is honest. He cited GOP Commissioner Kristine Svinicki, a former aide for Larry Craig (R-Idaho). "I have no problem with her, she told us who she is. I mean, you know, [Calif. Sen. Barbara] Boxer is upset at her because Boxer thinks she didn't level with her, but I have no problem with her, cause we knew what she was going in there: she was a tool of the industry. That's most everybody that's gone in there, so she had a qualification that fit into the past recipients of going to that agency."

Reid said that he wasn't looking to eviscerate Magwood and would have kept his concerns private if he hadn't been asked. "I have told Pete Rouse what I think, but no one publicly has ever asked me. I didn't feel it was appropriate to bring it up. You brought it up, and I do not have words to describe how little I think of this person. And as long as I have this job, he will never be chairman of anything that takes Senate confirmation."

CORRECTION: In an earlier version of this article, Larry Craig's political affiliation and state were listed incorrectly.

Negative campaigning has become more effective since 1828, though at times no less brutal. Many attribute this growing efficiency to the legacy of Republican strategist Lee Atwater. The former RNC chairman may have been best known as a driving force behind political ads such as the iconic <a href="http://www.youtube.com/watch?v=Io9KMSSEZ0Y" target="_hplink">Willie Horton commercial</a> against Michael Dukakis in 1988, but his past involvement in smear campaigns is much deeper. Slate <a href="http://www.slate.com/articles/arts/movies/2008/09/mr_wedge_issue.html" target="_hplink">reports</a> on Atwater's earlier career:
In 1973, the 22-year-old protégé of South Carolina Sen. Strom Thurmond began his consulting career by publicizing the fact that Tom Turnipseed, a candidate for the state Senate, had undergone shock therapy as a young man: "They hooked him up to jumper cables" became the catchphrase that sunk Turnipseed's candidacy. Five years later, Atwater helped to defeat Max Heller, a Holocaust survivor running for U.S. Congress, by secretly enlisting a third candidate to enter the race and stir up anti-Semitic sentiment. Atwater finagled his way into a minor post in the Reagan administration, but it was as the director of George H.W. Bush's 1988 presidential campaign (and mastermind of the Willie Horton TV ads) that he found his true Machiavellian voice.